Many commonly used motion detectors, such as those used to activate security outdoor lighting or indoor burglar alarms, detect only motion not obstructed by an intervening barrier. Also, these detectors respond only to motion, and do not track or provide the location of the object whose movement is sensed.
For certain applications, including but not limited to law enforcement, and fire and rescue, it is desirable to provide a portable, battery powered, apparatus capable of detecting a moving object through a barrier such as the wall of a closed room. To this end, motion detecting radar units have been developed which rely on a single radar transmitter and a single radar receiver to detect a moving object. Such devices suffer a number of deficiencies when employed to detect moving objects behind a barrier, such as the wall of a closed room. Although motion may be detected, the location of the moving object may remain a mystery.
U.S. Pat. No. 5,446,461 to Frazier discloses an imaging radar system having an antenna array for generating images of moving targets behind an obscuring structure. The data provided by this radar system is subject to background clutter which may result from internal walls and stationary objects present in an enclosed space.
Also, U.S. Pat. No. 5,345,240 to Frazier discloses a handheld motion detecting radar unit.
It is a primary object of the present invention to provide a novel and improved method and apparatus for detecting a moving object wherein motion of an object is mapped to provide the distance and bearing to the object.
Another object of the present invention is to provide a novel and improved method and apparatus for detecting a moving object using a radar system and antenna array for full waveform data acquisition and then accomplishing beam forming by combining the data from multiple transmitter/receiver combinations.
A further object of the present invention is to provide a novel and improved method and apparatus for detecting a moving object through a barrier wherein negative background influences are removed from data provided by a radar system and antenna array.
A still further object of the present invention is to provide a novel and improved method and apparatus for detecting a moving object through a barrier using a radar system and antenna array for full waveform data acquisition and then removing background influences from the acquired data before accomplishing beamforming.
These and other objects of the present invention are achieved by providing a novel and improved method and apparatus for detecting a moving object either directly with no intervening barrier or through a barrier by means of a radar system which acquires digital radar data using spatially separated antennas. These may constitute multiple transmitting antennas, multiple receiving antennas or multiple antenna transmitting and receiving (TR) pairs. The radar system must be one which provides full waveform radar data such that the data accurately represents the measurement of the propagating wavefield. Background data, which has been previously measured, is subtracted to enhance the received data. The data may be further enhanced by deconvolution which removes an estimate of the impulse response of the system, and then beamforming of the enhanced data is performed to compute an image. Finally, signal detection can be performed to identify and report the location of a detected object.